sclass SynchronizedCircularFifoBuffer<E> is Iterable<E>, IntSize {
  int capacity;
  long base;
  ArrayDeque<E> coreStorage; // Unsynched core list
  Cl<E> storage; // synched coreStorage
  
  *(int capacity) {
    this.capacity = capacity;
    coreStorage = new ArrayDeque<E>(capacity);
    storage = synchronizedCollection(coreStorage);
  }
  
  /**
   * Adds the given element to the buffer. If the buffer is full, the least recently added element is discarded so
   * that a new element can be inserted.
   */
  public void add(E e) {
    synchronized(storage) {
      if (isFull()) remove();
      coreStorage.addLast(e);
    }
  }
  
  /**
   * Removes and returns the least recently inserted element from this buffer.
   */
  public E remove() {
    synchronized(storage) {
      ++base;
      return coreStorage.removeFirst();
    }
  }
  
  /**
   * Returns true iff the buffers remaining capacity is 0.
   */
  public boolean isFull() {
    return storage.size() == capacity;
  }
  
  /**
   * Returns true iff the buffers size is 0.
   */
  public boolean isEmpty() {
    return storage.isEmpty();
  }
  
  /**
   * Returns the number of elements in the buffer.
   */
  public int size() {
    return storage.size();
  }
  
  public Object[] toArray() {
    return storage.toArray();
  }
  
  public<T> T[] toArray(T[] a) {
    return storage.toArray(a);
  }
  
  public List<E> asList() {
    return new ArrayList<E>(storage);
  }
  
  public Cl<E> getBackingStore() {
    ret storage;
  }
  
  public Iterator<E> iterator() {
    return storage.iterator();
  }
  
  public E last() {
    synchronized(storage) {
      ret coreStorage.peekLast();
    }
  }
  
  public void clear {
    synchronized(storage) {
      coreStorage.clear();
      base = 0;
    }
  }
  
  // how many elements were discarded
  synchronized long getBase() { ret base; }
  
  synchronized int getCapacity() { ret capacity; }
}

Began life as a copy of #1000774